Improvement in calipers



B. G. MARTIN.

No. 51,517. Patented Dec. 12, 18 65.

UNITED STATES PATENT OFFICO BENJN. G. MARTIN, PHILADELPHIA,PENNSYLVANIA, ASSIGNOR TO HIM- SELF, THOS. M. DAVIS, LLOYD H. WALTON,AND \VATSON SANFORD.

IMPROVEMENT IN CALIPERS.

Specification forming part of Letters Patent No. 5 L5 17, dated December12, 1865.

To all whom it may concern:

Be it known that I, BENJAMIN G. MARTIN, of the city of Philadelphia, inthe State of Pennsylvania, have invented a new and useful Improvement inMachinists Calipers; and I do hereby declare that the following is afull, clear, and exact description of the construction and operation ofthe same, reference being had to the accompanying; drawings, in whichThe Figures 1 and 2 represent the two opposite sides of the saidimproved calipers, like letters of reference indicating the same partswhen in the different figures.

The nature of my invention consists in the application of a pointedswinging bar to the pivot of a pair of calipers, having the lower edgesof its feet constructed so that when the said feet are closed togetheror have their heels in contact with each other their said lower edgeswill form a straight line in such relation to the swinging bar that-whenthe calipers,so closed, are held upright with the said edges on ahorizontal plane of any kind, the free pointed end of the swinging barwill coincide with another point fixed on one of the feet of thecalipers, and thus prove that the supporting-plane is truly horizontalor level.

In the drawings, A B represent the calipers, b 1) its feet, b 1) itsarms, 1) its pivot, G the swinging bar, and D the index.

The legs of the calipers A B are constructed and connected together by apivot-screw, b, in the usual well-known manner, but the feet I) I) aremade much longer than heretofore, and their bottom edges made so thatthey will be in a straight line with each other when their heels are incontact, as shown in Fig. 1. The heels serve as the contact-surfaces incaliper ing by inclosing the object.

The pointed swinging bar 0 is attached so as to swing freely on the samepivot, I), which unites the legs of the calipers, and fixed to the sideof the foot b of one of the legs is a thin plate, If, the upper end ofwhichis pointed and coincides with the point of the swinging bar 0 whenthe calipers are held in an upright position with their feet I) b incontact with each other and their lower edges on a horizontal plane ofany kind, as shown in Fig. 1."

The arms b b are extensions above the pivot b of the upper portions ofthe two parts of the calipers, A B, and are exactly of half the lengthof the legs, respectively, and constructed to have outside faces adaptedfor calipering within or between two surfaces, the said faces being alsoarranged so as to be touching each other when the heels of the feet I) bare in contact with each other, as shown in the same figure.

The index D is divided by equidistant radial lines, centering in bfl andfigured in two separate concentric series, d (1 the inner series offigures (1, indicating, when coinciding with the pointer (1 thedistances between the faces of the arms b N, and the outer series, d thedistances between the heels of the feet I) D211] calipering, and, thelength of the legs being double that of the arms, the same radial lineof the index D will indicate for both ends of the calipers, the numbersin the series (1 being half the value of those in (1 In this instancethe index is divided and numbered so as to represent inches and parts ofinches in the spaces between the respective measuringfaces of thecalipers.

It will be seen that these calipers will afford every facility that canbe required both in calipering and leveling, that they will serve alsoto ascertain whether a surface or line is plumb or not, by placing itsclosed feet I) 1) against the said surface or line and observing whetherthe swinging bar 0 coincides with the lines .1- g which are parallel tothe lower edges of the said closed feet, and that they can beconstructed at a very trifling increase of cost over the calipersheretofore used by machinists.

Having thus fully described and set forth my improved calipers, what Iclaim as new therein of my invention, and desire to secure by LettersPatent, is-

The application of a plumbing-bar, O, to a pair of calipers having feetZ) 11 constructed so as to form a straight line with each other when incontact, as and for the purpose described.

BENJAMIN GREEN MARTIN.

Witnesses:

BENJ. MORISON, B. F. SHATTUCK.

